Dental articulator.



. 1,173,046, Patented Feb. 22,1916.

D. M. SHAW.

DENTAL ARTICULATOR.

APPLICATION FILED SEPT. 2. 1915.

marten srarns earner oration.

DAVID M. SHAW, OF ELTHAM, ENGLAND, ASSIGNOR TO THE DENTAL MANUFACTURING COMPANY LIMITED, OF LONDON, ENGLAND.

DENTAL ARTICULATOR.

Original application filed April 15, 1914, Serial No. 831,977.

Specification of Letters Patent.

2, 1915. Serial No. 48,661.

To all whom it may concern:

Be it known that I, DAVID MACKINTOSH SHAW, a subject of the King of Great Britain, residing at 60 Beechill road, Eltham, in the county of Kent, England, have invented new and useful Improvements in and Relating to Dental Articulators, of which the following is a specification.

This invention forming a division to my copending application Serial No. 831,977, filed April 15, 1914, relates to improvements in dental articulator-s designed more particularly so that that portion of the instrument representing the human condyle is constructed to copy and carr 1 out exactly those characteristic translation movements of the natural condyle in a vertical plane which are known always to take place when the lower jaw is opened or shut upon the upper jaw. The exact reproduction of this particular movement is of practical importance because at least some degree of opening or shutting (vertical) movement takes place in all and every normal chewing movement, whether lateral, protrusive, or combinations of these movements. It is known that during this opening or shutting movement of the lower jaw upon the upper jaw there is always simultaneously a combined movement of translation and rotation in the lower jaw and condyles in such a way that when the movement of rotation about the condyles takes place with uniform velocity, the simultaneous movement of translation of the condyles themselves takes place with a variable velocity, which is slow or small in the beginning, quicker in the middle, and slower again at the end of the condyle path. It therefore follows that while this combined movement of the natural lower jaw may be at any instant resolved into a movement purely of rotation about a single point or axis, the position of this axis (called in kinematics the instantaneous center) changes from instant to instant relatively to any point fixed on the lower or the upper jaw, so that it cannot be represented by any fixed point. i I

In the older type of articulating frame or articulator with a purely pivotal and non} sliding joint, the artificial teeth required for either (upper or lower) jaw could be adjusted and arranged against the teeth of the opposing jaw only in that static or stationbut min a non-circular ary relationship of the shutteeth which dentists term occlusion, and so the correctness of their arrangement for efliciency in natural chewing movements could not possibly be tested with such simple hinge frames or articulators. To remedy this anatomical articulators were devised, the distinguishing feature of all of which is, that the joint which controls the movement of one jaw relative to the other imitates the natural aw joint in so far as to allow, in addition to the rotation or simple-hinge movement, a sliding movement of translation also. The aim of inventors has been to provide a joint mechanism by which the general character of the separate or combined movements of rotation and translation observed in the natural living jaw is imitated as closely as possible; and also so that any particular variation of the natural joint movement observed in an individual patient can be copied and reproduced in the articulator, with the prime object of insuring that artificial teeth arranged so as to oppose one another and act in a certain precise and efiicient manner during movements on the articular will be related and act in exactly the same manner during chewing movements in the mouth of that particular patient.

According to my invention I provide a dental articulator with a condyle part so constructed that during the movement of the arm carrying the lower jaw part with uniform angular velocity about the condyle, the condyle part moves in an undulated path with a velocity which varies in the natural manner from point to point of the movement, the motion being governed by means of a cam surface, and guideways for the condyle, so that the combined rotation and translation movements of the lower arm is not a movement of rotation about any fixed point as in other articulators, but takes place only about an instantaneous center, as in the natural It is thereby further effected that during the vertical opening and shutting movements'the translation path of the condyle part is not the arc of a circle as in some articulators hitherto constructed, or undulated path as in the natural human condyle. And, just as in the natural jaw, although the translation or sliding movement may take place by itself and without other movement whenever desired, it is impossible for any opening or shutting (vertical) movement to take place without a simultaneous movement of translation. Means are provided whereby the condyle path can be varied and adapted to agree with the ascertained path of any patient. I may also provide a mounting platform supported in such a position on the articulating apparatus that its surface represents the horizontal level and average position of the occlusal plane relative to the joint mechanism.

My invention is illustrated by way of example in the accompanying drawings, in which Figure 1 shows a perspective view of apparatus with a set of anatomical teeth set up in position. Fig. :2 shows a detail view of the cam construction for producing the correct natural motion of the condyle path in opening and shutting movements. Fig. 3 shows a detail view of a cam construction representing the longitudinal jaws in position of extreme opening. Fig. 4 shows a detail view of a locking pin for the curved guide ways. Fig. 5 shows a detail underside plan view of the upper arm of the articulator and the spring adapted to retain the cam surfaces on the lower arm against the engaging pins on the upper arm, and Fig. 6 shows a perspective view of the articulating apparatus with the mounting platform in position.

Referring now to the drawings-I provide condyles in the form of pins 1 extending inwardly and laterally from the curved cam surfaces 2 preferably on the lower arm of the instrument. The said pins 1 are adapted to engage in corresponding undulated open channels formed between a pair of cam members 3 preferably arranged in the upper arm respectively at a considerable distance below a pair of pins? on said upper arm. The pins 7 engage with the said curved cam surfaces 2 on the other arm of the articulator and the condyle movement is effected by the said pair of pins 7 being held in sliding contact with the said corresponding curved cam surfaces 2 attached to the other arm (preferably the lower) as shown.

The cam surfaces 2 on the lower arm of the articulator are normally retained in engagement with the pins 7 on the upper arm of the articulator by means of the leaf spring 8 on said upper arm (shown in detail in Fig. 5) doubled over upon itself, so that its free end 9 engages against the central portion of the cross bar 10 on the lower arm of the articulator arranged inside and between the condyle joints.

In order that the condyle path may bevaried and adapted to agree with the ascertained path of any patient, and yet the natu ral character of the accompanying movement be preserved, I allow for an adjustment of the curved guide channels by mounting said guide channel members 3 on pivots with horizontal arms so that the angular position of said guide channels can be varied to suit the condyle path of any patient. In connection with the pivots of said guide channel members 3 I provide locking pins 4, so that said cam channels are held rigidly in the position in which they are set. The front portion of the upper jaw member has an adjustable arm 16 directed vertically downward, the extremity of which rests when the jaw members are in the closed position upon the cam-shaped adjustable base 7 In combination with the articulating apparatus I may provide a mounting platform 6 as shown in Fig. 6 supported in such a position on the articulating apparatus that its surface represents the horizontal level and average relative position of the occlusal ilane. The said platform is employed only for those cases wherein it is not proposed to ascertain by individual measurements the exact position of the plaster jaws and occlusal plane relative to the joint. In use the upper bite-plate with attached plaster model is placed flat upon it, the medium line coinciding with the line scored upon the platform and the incisal point coming just to its front edge. No measurements are required. The said bite-plate may be held in position with a little wax or clay while the upper arm is being securely plastered down upon the cast.

\Vhat I claim is 1. In a dental articulator, the combination of an upper jaw member, a lower jaw member, condyles and undulated guides therefor connecting said jaw members, and

means including cooperating cams and pins on said jaw members all constructed to give sald condyles a variable velocity in the undulated guides during theopening or shutting movement of said jaw members.

2. In a dental articulator, the combination of an upper jaw member, a lower jaw member, condyles and undulated guides therefor, connecting said jaw members, pins on said upper jaw member and cam members on said lower jaw member engaging with said pins, said cam members being constructed to give said condyles during the opening or shutting movement of said jaw members, a variable velocity in their guides, which is slow at the beginning, quicker in the middle and slower again at the end of travel in said guides.

3. In a dental articulator, the combination of an upper jaw member, a lower jaw member, condyles mounted in one of said jaw members, two open guideways for said condyles, mounted in the other of said jaw members, locking pins adapted to hold said condyles in the angle at which they are set,

' tion of an upper jaw member,

and cams adapted to control the condyles so that the latter move with the variable velocity during the movement of said jaw members. I

4. In a dental articulator, the combination of an upper jaw member, a lower jaw member, condyles and members having cam shaped guideways for said condyles connecting said jaw members, said guideway members being mounted on pivots in one of said jaw members, locking pins adapted to hold said guideway members at the angle at which they are set, and means on said jaw members to control the condyles so that the latter travel in the undulated guideways during the occlusal movement of said jaw members.

5. In adental articulator, the combinaa lower jaw member, condyle pins on said lower jaw member, a pair of cam shaped guideway members on said upper jaw member adapted to receive said condyle pins, controlling means on said jaw members constructed to gij e said condyle pins a variable velocity in the cam shaped guideway members which velocity is slow at the beginning, quicker at the middle and slower again at the end.

6. In a dental articulator, the combination of an upper jaw member, a lower jaw member, condyle pins on said lower jaw member, pivots in said upper jaw member,

Copies of this patent may be obtained for five cents each, by addressing the a pair of guides for each condyle pin forming an undulated path between them open at both ends, said guides being mounted on said pivots and adapted to receive said condyle pins, locking pins adapted to hold the pivots at an angle in which said guides are set, and controlling means on said jaw members constructed to give said condyle pins a variable velocity in said guide paths, which velocity is slow at the beginning, quicker in the middle and slower again at the end of their paths.

7. In a dental articulator, the combination of an upper jaw member, a lower jaw member, condyles and a pair of undulated guides for each condyle connecting said jaw members, controlling means on said jaw members constructed to give said condyles a variable velocity in the undulated guides during the opening and shutting movements of said jaw members, said velocity being slow at the beginning, quicker in the middle, and slower again at the end of travel in the guides, and a mounting platform supported on said lower jaw member in such a position that its surface represents the horizontal level and average relative position of the occlusal plane.

D. M. SHAW. WVitnesses:

ARTHUR J. STEPHENS,

LEONARD E. HAYNES.

Commissioner of Patents,

Washington, D. 0. 

